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The present invention pertains to process for preparing nucleoside phosphoramidates and their intermediates. Phosphoramidates are inhibitors of RNA-dependent RNA viral replication and are useful as inhibitors of HCV NS5B polymerase, as inhibitors of HCV replication and for treatment of hepatitis C infection in mammals. One of the recently approved phosphoramidate by USFDA is Sofosbuvir [1190307-88-0]. Sofosbuvir is a component of the first all-oral, interferon-free regimen approved for treating chronic hepatitis C. The present invention provides novel intermediate, its process for preparation and use for the preparation of Sofosbuvir. The present invention also gives one pot process for preparation of Sofosbuvir.

Hepatitis C virus (HCV) infection is a major health problem that leads to chronic liver disease, such as cirrhosis and hepatocellular carcinoma, in a substantial number of infected individuals. There are limited treatment options for individuals infected with hepatitis C virus. The current approved therapeutic option is the use of immunotherapy with recombinant interferon- [alpha] alone or in combination with the nucleoside analog ribavirin.

Another object of the present invention is to provide a process to prepare the intermediate of Formula 2.

Another object of the present invention is use of the intermediate of Formula 2 in the preparation of Sofosbuvir of Formula 1.

Formula 1

Example 1:

Process for the preparation of S-oxazolidinone derivative of Formula 2

Step-1 Preparation of phosphorochloridate solution:

Dichloromethane (DCM 400ml) was charged in round bottom flask flushed with nitrogen. Phenyl phosphodichloridate (18.30ml) was added in one portion in the flask. The flask was cooled to -60°-70°C with a dry ice-acetone bath. Solution of L-alanine isopropyl ester hydrochloride (20.6gm)) in DCM (50ml) was added to the reaction flask. To this was added a solution of triethylamine (11.20ml) in MDC (100 ml) was added over a course of 60 minutes, while maintaining internal temperature below -70 °C throughout the addition. After completion of reaction, temperature of reaction mass was raised to room temperature.

100ml THF was charged in another round bottom flask flushed with nitrogen followed by the addition of S-4-phenyloxazolidnone (lOgm). Triethyl-amine (11.2ml) & LiCl (2.85gm) were added to the above flask. The reaction mass was stirred for 15-30 min at room temperature and was cooled to 0-5 °C. Phosphorochloridate solution from step-1 was added drop- wise to the reaction flask in 15-45 min maintaining reaction temperature at 0-5 °C. The reaction mass was stirred for 30-60min at 0°-5°C. The reaction progress was monitored on thin layer chromatography. After completion of the reaction, the reaction temperature was raised to room temperature. Agitation was resumed for an additional 30min. The reaction mass was filtered and concentrated under reduced pressure. To this was added diisopropyl ether (400ml) and aqueous saturated ammonium chloride solution and reaction mass was stirred for 10-15 minutes. Organic layer was separated and was washed with water (100ml) & dried over sodium sulfate and concentrated under vacuum. Cyclohexane (50ml) was charged to the obtained oily mass and reaction mass was stirred till solid precipitated out. Solid was filtered and washed with cyclohexane and dried under vacuum (8.80gm MP 56.5°-56.6°C). The obtained product was characterized by mass, NMR & IR. 1H NMR (DMSO-d6) δ 1.142 -1.18

Example 3: Process for the preparation of Sofosbuvir by coupling of isopropyl(((3-nitro-5-(trifluromethyl)pyridin-2-yl)oxy)phenoxy)phosphoryl-L-alaninate with 1-((2R,3R,4R,5R)-3-fluoro-4-hydroxy-5-(hydroxymethyl)-3-methyltetrahydrofuran-2-yl)pyrimidine-2,4(lH,3H)-dione :

To a solution of l-((2R,3R,4R,5R)-3-fluoro-4-hydroxy-5-(hydroxymethyl)-3-methyltetrahydrofuran-2-yl)pyrimidine-2,4(lH,3H)-dione (0.2gm) in THF (4 ml), tert- butylmagnesium chloride (0.80ml, 1.7 M solution in THF) was added dropwise at room temperature and reaction mass was stirred for 30 minutes. A solution of pyridine derivative from example 2 (0.36gm) in THF (4ml) was added dropwise to the reaction mass at room temperature. Completion of reaction was monitored using TLC. After completion of reaction, reaction mass was quenched by using saturated ammonium chloride solution (10ml). Reaction mass was extracted with ethyl acetate (50ml). Organic layer was separated, dried over magnesium sulfate and concentrated under vacuum. The resulting residue was purified by column chromatography on silica gel & obtained solid product was characterized. MS, m/e 530.2 (M+l) +.

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DR ANTHONY MELVIN CRASTO, Born in Mumbai in 1964 and graduated from Mumbai University, Completed his Ph.D from ICT, 1991,Matunga, Mumbai, India, in Organic Chemistry, The thesis topic was Synthesis of Novel Pyrethroid Analogues, Currently he is working with GLENMARK PHARMACEUTICALS LTD, Research Centre as Principal Scientist, Process Research (bulk actives) at Mahape, Navi Mumbai, India. Total Industry exp 29 plus yrs, Prior to joining Glenmark, he has worked with major multinationals like Hoechst Marion Roussel, now Sanofi, Searle India Ltd, now RPG lifesciences, etc. He has worked with notable scientists like Dr K Nagarajan, Dr Ralph Stapel, Prof S Seshadri etc, He did custom synthesis for major multinationals in his career like BASF, Novartis, Sanofi, etc., He has worked in Discovery, Natural products, Bulk drugs, Generics, Intermediates, Fine chemicals, Neutraceuticals, GMP, Scaleups, etc, he is now helping millions, has 9 million plus hits on Google on all Organic chemistry websites. His friends call him worlddrugtracker. His New Drug Approvals, Green Chemistry International, All about drugs, Eurekamoments, Organic spectroscopy international,
etc in organic chemistry are some most read blogs He has hands on experience in initiation and developing novel routes for drug molecules
and implementation them on commercial scale over a 29 year tenure till date Aug 2016, Around 30 plus products in his career. He has good knowledge of IPM, GMP, Regulatory aspects, he has several International patents published worldwide . He has good proficiency in Technology transfer, Spectroscopy, Stereochemistry, Synthesis, Polymorphism etc., He suffered a paralytic stroke/ Acute Transverse mylitis in Dec 2007 and is 90 %Paralysed, He is bound to a wheelchair, this seems to have injected feul in him to help chemists all around the world, he is more active than before and is pushing boundaries, He has 9 million plus hits on Google, 2.5 lakh plus connections on all networking sites, 25 Lakh plus views on dozen plus blogs, He makes himself available to all, contact him on +91 9323115463, email amcrasto@gmail.com, Twitter, @amcrasto , He lives and will die for his family, 90% paralysis cannot kill his soul., Notably he has 13 lakh plus views on New Drug Approvals Blog in 212 countries......https://newdrugapprovals.wordpress.com/ , He appreciates the help he gets from one and all, Friends, Family, Glenmark, Readers, Wellwishers, Doctors, Drug authorities, His Contacts, Physiotherapist, etc

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